doc-rst: document enum symbols

doc-rst: document enum symbols

After checking that all enum fields are documented at the
corresponding table on the rst file, let's point to the
table, instead of ignore the symbols.

A few symbols are not meant to be documented, as they're
deprecated stuff. keep ignoring them.

One enum field is not documented. Either it is obsolete
or a documentation gap. So, produce warnings for it.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>